System and method of surfacing a lens, such as a lens for use with eyeglasses

ABSTRACT

A system and method of forming surfaces on eyeglass lenses is described. In some examples, the surface is a spherical, cylindrical or spherocylindrical surface at a center of the lens and an aspherical surface at a periphery of the lens. In some examples, forming the surface on the lens reduces the thickness of the lens at the periphery of the lens.

BACKGROUND

Traditionally, the manufacturing of a lens for use in eyeglassesrequires a number of steps, including:

-   -   choosing a semi-finished lens blank with a finished front        surface (base curve) and an unfinished back surface,    -   grinding the back surface with a lathe, such as a toric lathe,        that creates a spherical concave or convex surface (such as a        cylindrical or spherical surface) on the back surface to place        an optical system on the surface used to correct the vision of a        user of eyeglasses, and    -   lapping the back surface to smooth the surface to a desired        curvature to finish the optical system.

Typically, the curvature of the back surface is limited to the size ofthe lap piece. For example, laps are generally produced to createcurvatures on lens surfaces. The laps are formed to produce a specificcurvature on a surface, although curvatures placed on differentcorrective lenses, due to the inherent limitations of creating the laps,may be incrementally different (that is, the minimum difference incurvature between two lenses may be around 0.125 diopters). Thus, usinglathes and laps, the creation of surfaces on lens has often been limitedin surface type (generally spherical surfaces) and in specification ofthe curvature (generally incremental from one lens to a next lens).

Additionally, lenses having a strong prescription (such as thoserequiring large radii of curvature) are often bulky and inconvenient toa user wearing eyeglasses with such lenses. These users may suffer fromthe “coke bottle effect,” where the thickness of the lens causes theeyeglasses (and the user wearing them) to look unattractive at theperiphery of the lenses. These and other problems exist with respect tocurrent eyeglass lens manufacturing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a cross-sectional view of a lens usedin eyeglasses having an aspherically curved surface.

FIG. 2 is a diagram illustrating a cross-sectional view of analternative lens used in eyeglasses having an aspherically curvedsurface.

FIG. 3 is a flow diagram illustrating a process of manufacturing anaspherical lens.

FIG. 4A is a flow diagram illustrating a process of determining a backsurface of an aspherical lens.

FIG. 4B is a diagram illustrating an exemplary hyperbolic curve.

FIGS. 5A-5D are block diagrams illustrating example stages ofmanufacturing an aspherical lens.

FIG. 6 is a flow diagram illustrating a process of forming aprescription eyeglass lens.

FIG. 7 is a diagram illustrating a prescription order form.

DETAILED DESCRIPTION

A system and method for creating aspherical, custom-designed backsurfaces on lenses used in eyeglasses is described. In some examples,the system creates a surface on a lens having a specified radius ofcurvature at the center along with a thinner portion at the periphery ofthe lens. The system may produce curves on lens surfaces thatnon-spherically change in curvature from the center of the lens to theperiphery. For example, the system may create conic-based surfaces, suchas hyperbolic surfaces, that are substantially spherical, cylindrical,or spherocylindrical at a center point and substantially aspherical awayfrom the center point.

In some cases, the system may employ digital surfacing in creating thecurves on the lens surfaces. Digital surfacing, and other soft toolbased surfacing, is a relatively new manufacturing technique in theindustry that allows manufacturers to create an infinite number ofsurfaces on lenses, unlike previous lathing and lapping techniquesdescribed herein. For example, using digital surfacing, a diamond orother type of cutter produces a back surface of a lens according to aspecified depth, at a precision of one tenth of a micron or less. Thus,digital surfacing, in some cases, enables manufacturers to createnon-spherical surfaces on lenses.

In some cases, the system may provide manufacturers and other eye careprofessionals with simple adaptable prescriptions for patients, allowingthe eye care professionals to easily create unique lenses that providecosmetic, optical, and other benefits. For example, a prescription for apatient may define (1) a specific conic curve (or similar curve) thathas a centrally located radius of curvature that may satisfy the opticalneeds of a patient and a (2) peripherally defined thickness of the lensthat may satisfy the cosmetic needs of the patient.

Where previous techniques of creating concentric spheres across asurface (using lathes and laps) could not achieve such detailedrequirements, forming conic sections on the back surfaces of lensesenables professionals to create lenses having patient specific opticaland cosmetic benefits, while still maximizing the optical quality of thelenses.

Various examples of the technology will now be described. The followingdescription provides specific details for a thorough understanding andenabling description of these examples. One skilled in the art willunderstand, however, that the technology may be practiced without manyof these details. Additionally, some well-known structures or functionsmay not be shown or described in detail, so as to avoid unnecessarilyobscuring the relevant description of the various examples.

The terminology used in the description presented below is intended tobe interpreted in its broadest reasonable manner, even though it isbeing used in conjunction with a detailed description of certainspecific examples of the technology. Certain terms may even beemphasized below; however, any terminology intended to be interpreted inany restricted manner will be overtly and specifically defined as suchin this Detailed Description section.

Examples of Lenses

As described herein, aspects of the system and method enable eyeglassmanufacturers and other eye care professionals to apply prescriptions tothe back surfaces of lenses while tailoring the peripheries of thelenses to meet the needs of their patients. Many patients require strongcorrections (e.g., those greater than ±5.0 diopters), and may benefitfrom reducing the thickness of their lenses where possible. FIG. 1 showsa cross-sectional view of a concave lens 100 used in eyeglasses havingan aspherically curved surface formed in accordance with the methoddisclosed herein. Lens 100 is a concave or minus lens, and is often usedto correct nearsightedness in patients. Lens 100 has a back surface 110and a front surface 120. Lens 100 may be a spherical lens, a cylindricallens, or a spherocylindrical lens. The front surface 120 may be aspherical or aspherical curve, depending on the type of lens or type ofcorrections required for the eyeglass wearer. The back surface 110 iscurved to meet the needs of the patient's prescription. At an opticalcenter of the lens 112, the lens is spherically curved based on aprescribed correction. For example, lens 100 has a certain curvature atcenter 112 based on the radius of a circle defined by line 113.

The optical center of the lens is not necessarily the center of thelens. Often, the optical center is placed in front of a patient's pupil,in order to provide the best focus correction to the patient. In somecases, the optical center for a lens may be different for a patient'sright eye than for the patient's left eye. Therefore, the optical centeris often determined for each eye of a patient.

In typical eyeglass lenses, a back or rear surface of a lens follows theedge of the circle that defines the curvature of the lens. That is, thelens is spherical both at the center and at the periphery. However, inthis case, the back surface 110 of the lens, at periphery 114, does notfollow the circle that defines the radius of curvature. Instead, thesaggital depth of the lens is reduced at or near the periphery, and theback surface 110 of the lens at the periphery 114 is asphericallycurved. The thickness is reduced at the periphery, creating a lens thatprovides a prescribed optical correction to a patient without thedrawbacks typical of thick lenses (e.g., unattractive, cumbersome,heavy, causes “image jump,” and so on). For example, the asphericalcurve at the periphery may be substantially similar to the curve of thefront surface 120.

Additionally, in some cases, by thinning the lens and therefore changingthe optical power at the periphery (thinning causes the radius ofcurvature to change), the lens may provide a patient with enhanced oradvantageous optical properties (such as improved focus correction)through the peripheral portion of the lens.

Although the method of shaping lenses has been described herein withrespect to concave lenses, some or all aspects of the system may beapplied to convex lenses. FIG. 2 shows a cross-sectional view of aconvex lens 200 used in eyeglasses having an aspherically curvedsurface. Lens 200 is a convex or plus lens, and is often used to correctfarsightedness in patients. Lens 200 has a back surface 210 and a frontsurface 220. The front surface 220 may be a spherical or asphericalcurve, depending on the type of lens or type of corrections required forthe eyeglass wearer. The back surface 210 is curved to meet the needs ofthe patient's prescription. At an optical center of the lens 212, thelens is spherically curved based on a prescribed correction. Forexample, lens 200 has a certain curvature at center 212 based on theradius of a circle defined by line 213. In this example, the lens, atperiphery 214, does not follow the circle. Instead, the saggital depthof the back surface 210 of the lens may be modified such that the backsurface 210 of the lens at the periphery 214 is aspherically curved,while the back surface 210 at the optical center remains substantiallysimilar to the optical center on line 213. In some cases, back surface210 and line 213 approximately intersect at the edge 215 of the lens atthe same point. However, the lens formed between 220 and 210 may bethinner in the center. Thus, in these cases, the thinning of the lens200 occurs at or near the optical center 212, and not at the periphery214 (e.g., at the edge 215). Similar to the concave lens 100 describedherein, thinning the convex lens 200 provides a patient with a lens thatsatisfies a prescribed correction without the drawbacks associatedtherewith.

Of course, in addition to the lenses described herein, the system may beemployed with other lenses. For example, the system may be applied tothe front surfaces of lenses (such as lenses that are aspheric due tochanges in the front surface of the lens) and to combination lenses,such as sphero-cylindrical lenses. Examples of other lens that may beemployed by the system include biconvex lenses, biconcave lenses,planoconcave lenses, planoconvex lenses, meniscus lenses, concave-convexlenses, cylindrical lenses, and so on.

Also, varying a refractive index of a lens varies the optical power ofthe lens. Therefore, the system may factor in or take into account therefractive index of a lens when determining how to modify the thicknessof a lens at the periphery.

Additionally, although the above examples show a two-dimensionalcross-section of a lens, the system may be employed at different crosssections of a single lens. That is, the system may create a surface on alens that has one peripheral thickness at a first cross-section and adifferent peripheral thickness at a second cross-section. The lens mayhave many different thicknesses at a certain radial distance from theoptical center, depending on the needs of the patient. For example, thesystem may create a back surface from many different two-dimensionalaspherical curves combined to create an aspherical three-dimensionalsurface.

Creating an Aspherical Surface on a Lens

As described herein, the system creates aspherical surfaces on lenses inorder to provide lenses with prescribed optical corrections and enhancedcosmetic appearances. FIG. 3 illustrates a routine 300 for manufacturingan aspherical lens. In step 310, a lens manufacturer or eye careprofessional (such as an optician creating lenses at an eyeglass vendor)chooses a lens blank having a pre-determined characteristic, such as abase curve on the front surface of the lens blank. Lens blanks may beprecut lenses having base curves of varying intervals of correction(e.g., −1.0 D, −2.0 D, and so on) that provide a starting point for aneye care professional. An eye care professional, upon receiving aprescription for a patient, may choose a suitable lens blank to begincreating the patient's prescribed lens.

In step 320, the eye care professional, another person, or a computingsystem or computer application associated with the eye care professionaldetermines the surface to be applied to the back surface of the lensblank. For example, the prescription may require a spherical surface atan optical center of the lens and an aspherical surface at or near aperiphery of the lens. Further details with respect to determining thesurface will be discussed with respect to FIGS. 4A-4B.

Referring to FIG. 4A, a flow diagram illustrating a routine 400 ofdetermining a surface of an aspherical lens is shown. In step 410,routine 400 determines a radius of curvature to apply at the opticalcenter of the back surface of the lens. For example, the eye careprofessional may receive a prescription that defines the radius ofcurvature. In step 420, routine 400 determines a point or points betweenthe optical center and the periphery of the lens and a thicknessrequirement at these points, such as one point, a few points, or a ringof points from the optical center. For example, routine 400 may receiveinstructions to reduce the thickness at a certain radial distance fromthe optical center, and determine a point at the radial distance withinthe lens that provides the required thickness. In step 430, routine 400determines or fits a curve that substantially conforms to the radius ofcurvature determined in step 410 and to the point(s) determined in step420. For example, the system may determine the best fit curve is ahyperbola that substantially conforms to the radius of curvature andsubstantially passes through or fits the determined points. The systemmay also determine the curve to be an ellipse (or portion of anellipse). The system, therefore, may determine the curve to be ahyperbola, parabola, ellipse, or other conic section suitable to satisfythe determined characteristics. In these cases, the curve will besubstantially spherical at or near the optical center of the lens andsubstantially aspherical at or near the periphery.

For example, a prescription calls for a corrective lens having an indexof refraction of 1.53 and a radius of curvature of −6.0 diopters (D) onthe back surface of the lens (the surface closer to the eye of apatient). In this case, such a prescription causes the periphery to beundesirably thick. Therefore, in addition to the correctiverequirements, the prescription also indicates that the lens should bethinned near the edges (e.g., 50 mm from the optical center of the lens)in order to reduce the radius of curvature 1 diopter, to −5.0 D.Therefore, the prescription calls for a back surface having a radius ofcurvature of −6.0 D at 0 mm from the optical center of the lens, and aradius of curvature of −5.0 D at 50 mm from the optical center of thelens in all directions (that is, at all points around the center).Fitting a curve that substantially satisfies these requirements willcause the back surface to be substantially spherical at the opticalcenter and substantially aspherical at the periphery of the lens.

We can find a hyperbolic curve that satisfies these requirements for theback surface. Referring to FIG. 4B, a graph of a hyperbola 440 is shown.The lower half of the hyperbola is placed with foci along the y-axis(also the axis that pass through the optical center of the lens in thisexample). Using a curvature formula for the hyperbola, and given apredetermined radius of curvature and desired thickness of the lens(y-a) at a certain distance from the center (d), we can determinehyperbolic curves to be applied to the back surface in all directions.In the current example, the radius of curvature is =−6.0 D at 0 mm and−5.0 D at 50 mm. Thus, we can determine the value of the focus (for thelower half curve) to be approximately 8.2 mm. Using the value for thefocus, we can then find values for thinning the saggital depth (a) atvarious distances from the center of the hyperbola. For example, at d=5mm the saggital depth is about 0.1 mm, and at d=20 mm the saggital depthis about 2.2 mm. Thus, we determine hyperbolic curves that substantiallyfit these points and create a back surface for a lens that provides theprescribed radius of curvature with desired peripheral changes.

Of course, as described herein, other curves may be employed by thesystem. For example, the system may determine that other conics best fita required radius of curvature and saggital depths, as described herein.In addition, the system may create two or more curves that satisfy theprescribed requirements. For example, the system may use piecewisefunctions, where one of the functions fits the spherical radius ofcurvature at the center of the lens and the other functions fit theaspherical periphery. Also, the system may create more than one curvewhen forming the lens surface. As lenses are three-dimensional, thesystem may create many curves in two dimensions that combined form athree-dimensional surface.

Referring back to FIG. 3, after a curve and or surface is determined,such as using the methods described with respect to FIG. 4A-4B, routine300 applies the surface to the back surface of the lens. In thisexample, the back surface is the surface closer to the patient. However,as described herein, the system may apply the surface to the frontsurface of the lens as well, or to both surfaces.

In order to apply a continuous, even surface, the system may employdigital surfacing or other similar techniques. As described herein,using lathes and laps does not allow for the implementation of a conicsurface onto the lens. Digital surfacing, however, enables the system toform conic or conic-based surfaces on lenses that provide the requiredoptical corrections and peripheral enhancements.

Developing Lenses for Patients

In order to convey the creation of the aspherical surfaces describedherein to eye care professionals, the system may provide a fewparameters when defining a prescription. FIGS. 5A-5D illustrate theprocess of defining requirements of an aspherical lens with a reducedperipheral thickness.

For example, in FIG. 5A, the system creates a lens 510 having a backsurface 520 curved (such as spherically curved) with a radius ofcurvature 530 equal to R. In FIG. 5B, the system determines a radialdistance 540 equal to D at a point on surface 520 of the lens 510. InFIG. 530, the system determines a point having a saggital depth 550equal to S.D. at the radial distance D. Finally, in FIG. 5D, the systemcreates a curve 555 that fits the point at the saggital depth 550. Thus,as shown in the Figure, a portion 560 of the lens is removed in order tocreate the new curve 555 at the desired depth S.D. at the radialdistance D.

FIG. 6 illustrates a routine 600 that summarizes the steps performed byan eye care professional in creating the lenses described herein. Instep 610, the professional receives a prescription for the lens. Theprescription may provide information related to a type of lens, amaterial for the lens, which eye, a spherical or cylindrical correction,and so on. For example, the routine 600 receives a prescription for aspherical correction of −4.0 diopters for the left eye.

In step 620, the eye care professional receives an adjustment for theperiphery of the lens. The adjustment may provide information related tothe placement of the adjustment, such as at what radial length from theoptical center of the lens or at what direction of the lens, or it mayinclude a general characterization of the adjustment, such as “reducethe saggital depth” at the periphery. In addition, the adjustment mayprovide information related to the thickness reduction. The adjustmentmay be specified in a variety of ways. For example, the adjustment maydefine a certain optical power adjustment (e.g., reduce −1.0 D at 30mm), a certain percentage (e.g., reduce 30% at 35 mm), a certaindistance (e.g., reduce 3 mm at 35 mm), and so on. Additionally, theadjustment may be a general specification that does not necessarilydefine the exact adjustment. For example, the adjustment may be a “smallreduction of lens thickness,” a “an average reduction,” a “largereduction,” and so on.

In step 630, the eye care professional creates the lens using theprescription and any periphery adjustments. Thus, a simple method ofdefining the parameters of a lens for use in eyeglasses is created.

Adjustment information may be provided to eye care professionals in avariety of ways. For example, the system may use a computer application,and add fields directed to reducing the thickness of the lens in thecomputer application. Additionally, the system may create prescriptionpads or other similar paper-based products commonly used by eye doctorsand other eye care professionals.

For example, FIG. 7 is a diagram illustrating a prescription order form700 that may be implemented as a prescription pad or into a computerapplication. Form 700 may include typical information found inprescriptions, such as a patient name 710, date 712 and other personalinformation (address, phone number and so on). Form 700 may also includeprescription information, such as information 720 related to distancevision (D.V.) or near vision (N.V.), information 730 related to the eye(O.D. for right eye or O.S. for left eye) and the recommended correction740. For example, in form 700, a doctor prescribes a sphericalcorrection of −5.25 D for the right eye of a patient.

Form 700 may also contain periphery reduction information 750, asdescribed herein. For example, the form 700 may define a reduction of+2.0 D at a radial distance of 40 mm for the right eye lens, and areduction of 30% at 50 mm for the left eye lens.

Thus, the system may be integrated into other typical prescription formsand applications, enabling eye care professionals to create these lensesin a similar fashion to lenses that do not require peripheraladjustments, among other benefits.

Conclusion

Thus, the system and method creates custom-specified, prescriptionaspheric surfaces having reduced peripheries on lenses for eyeglasses.In forming these aspheric surfaces on the back surfaces of lenses (thesurfaces closer to the eye), the system is able to place the center ofasphericity anywhere on the lens. Reducing the thicknesses provides manybenefits, such as thinner and more attractive lenses, lighter lenses,visual enhancements (such as when thinning counteracts magnification atthe edges of a lens or reduces “image jump” or the “jack-in-the-box”effect), and other benefits.

The above detailed description of embodiments of the system is notintended to be exhaustive or to limit the system to the precise formdisclosed above. While specific embodiments of, and examples for, thesystem are described above for illustrative purposes, various equivalentmodifications are possible within the scope of the system, as thoseskilled in the relevant art will recognize. Accordingly, the technologyis not limited except as by the appended claims.

1. A spherocylindrical lens for use with eyeglasses, the lens having afront surface and a back surface, wherein the back surface comprises: afirst portion having a first radius of curvature, wherein the firstportion contains an optical center of the back surface of the lens; anda second portion having a second radius of curvature different than thefirst radius of curvature, wherein the second portion surrounds thefirst portion and is bounded by a periphery of the back surface of thelens, and wherein the first portion and second portion are formed of acontiguous piece of lens material using digital surfacing.
 2. Thespherocylindrical lens of claim 1, wherein a length of the first radiusof curvature is lesser than a length of the second radius of curvature.3. The spherocylindrical lens of claim 1, wherein the back surface ofthe lens is a concave surface.
 4. The spherocylindrical lens of claim 1,wherein the back surface of the lens is a convex surface.
 5. Thespherocylindrical lens of claim 1, wherein the second portion of theback surface has a third radius of curvature different than the firstradius of curvature and the second radius of curvature.
 6. Thespherocylindrical lens of claim 1, wherein the second portion of theback surface includes: a first point located on the back surface andalong a line extending from the optical center in a first direction,wherein the first point is located at a first depth measured withrespect to a location of a point on the back surface and at the opticalcenter; and a second point located on the back surface and along a lineextending from the optical center in a second direction, wherein thesecond point is located at a second depth different than the first depthmeasured with respect to a location of the point at the optical center.7. The spherocylindrical lens of claim 1, wherein at least onecross-section of the back surface is defined by a substantiallyhyperbolic curve.
 8. The spherocylindrical lens of claim 1, wherein atleast two cross-sections of the back surface are defined bysubstantially hyperbolic curves.
 9. The spherocylindrical lens of claim1, wherein the back surface includes: a first cross-section of the backsurface defined by a first substantially hyperbolic curve; and a secondcross-section of the back surface defined by a second substantiallyhyperbolic curve different than the first substantially hyperboliccurve.
 10. The spherocylindrical lens of claim 1, wherein the secondradius of curvature is substantially similar to a radius of curvature ofthe front surface of the lens.
 11. A method of specifying a lens shapeon an inner side of a lens for use in prescription eyeglasses, whereinthe inner side is a side closer to a user of the eyeglasses, whereinspecifying the lens shape includes: determining an optical center of thelens, wherein the optical center is related to a position of the innerside of the lens with respect to an eye of the user of the eyeglasses;and defining a curve that radiates from a point at the optical center ofthe lens to a periphery of the lens, wherein defining a curve includes:determining a radius of curvature at the optical center of the lens,wherein the radius of curvature relates to an optical prescription forthe user; identifying one or more points at the periphery of the lens,wherein the one or more points are located at a different radius ofcurvature than the radius of curvature at the optical center; andfitting a substantially conic function through the point at the opticalcenter and through the one or more points at the periphery of the lens,wherein the defined lens has one radius of curvature at the opticalcenter and a second radius of curvature at the periphery.
 12. The methodof claim 11, wherein the substantially conic section is a hyperboliccurve.
 13. The method of claim 11, further comprising: applying thesubstantially conic function to the surface using digital surfacingtechniques.
 14. The method of claim 11, wherein identifying one or morepoints at the periphery of the lens includes: identifying a first pointhaving a first radius of curvature at a first direction from the pointat the optical center; and identifying a second point having a secondradius of curvature different than the first radius of curvature at asecond direction from the point at the optical center.
 15. A method ofproviding instructions to a lens surfacing apparatus, the methodcomprising: defining an optical correction parameter at an opticalcenter point located on a back surface of a lens, wherein the opticalcorrection parameter defines the back surface as a three-dimensionalsurface having a uniform radius of curvature at all points on thesurface; defining a saggital depth adjustment for a ring of pointslocated on the back surface of the lens at specified radial distancesfrom the optical center point, wherein the saggital depth adjustmentdefines an adjusted ring points not located on the back surface; andinstructing the lens surfacing apparatus to create an adjusted backsurface defined by a substantially conic section that includes theradius of curvature at the optical center point and the adjusted ring ofpoints.
 16. The method of claim 15, wherein the adjusted back surface isa substantially hyperbolic surface.
 17. The method of claim 15, whereinthe adjusted back surface is a substantially parabolic surface.
 18. Themethod of claim 15, wherein the adjusted back surface is a substantiallyelliptical surface.
 19. The method of claim 15, wherein the adjustedback surface is a surface created by two or more different conicsections.
 20. The method of claim 15, wherein the ring of points formsan ellipse.
 21. A method of prescribing a corrective lens for a user ofeyeglasses, the method comprising: defining a radius of curvature for arear surface of the lens to be located at an optical center of the lens,wherein the radius of curvature is chosen based on information relatedto an examination of an eye of the user; and defining one or moreadjustments to the radius of curvature at one or more points not locatedat the optical center of the lens, wherein the adjustments to the radiusof curvature modify a thickness of the lens at the one or more points.